The invention relates to a method and device in for generating an error signal in connection with the coherent heterodyne reception of lightwaves.
A device with a local laser and two detectors is known from. European Laid-Open Document EP-0 831 604 A1 for checking the optical alignment of two lightwaves in connection With coherent heterodyne reception, each of which includes two identical detector halves, which are respectively separated by a strip shaped interruption or by gaps in the surface of the photodiode electrode, wherein the gaps in the two detectors are arranged orthogonally in respect to each other. This device is employed as a direction-selective optical monomode receiver. In this case, blocking is provided in a receiving telescope of this device as well as in the beam path of the local laser. This permits the generation of an error signal for a spatial beam regulation of an optical heterodyne receiver with a good signal-to-noise ratio, while avoiding to the greatest degree possible systematic losses, and while at the same time interfering as little as possible with the data signal to be transmitted.
An optical bench is furthermore known from European Laid-Open Document EP-0 844 473 A1, whose bench structure is such that, in case of a heat distortion of arms provided for the connection of the support elements of various optical units, the support elements can be displaced without tilting transversely in respect to axes, which have defined angular positions in respect to each other and to the bench structure. Such an optical bench can be combined with the device mentioned at the outset.
Although such a xe2x80x9ctracking sensorxe2x80x9d method permits the simultaneous communication and determination of the spatial tracking error, the appropriate device has been shown to be disadvantageous on account of the relatively large adjustment outlay during its production.
It is therefore the object of the invention to create a method and a device for the generation of an error signal in connection with the coherent heterodyne reception of lightwaves, which results in a simpler adjustment of such a system.
A device is used for generating error signals for regulating the optical alignment of two lightwaves in connection with coherent heterodyne reception and comprises a receiver device arranged focused opposite a front face at the end of a lightwave fiber in order make possible the transmission of the received information lightwave through the lightwave fiber to an optical waveguide coupler, which is connected via a further lightwave fiber with a local laser and via two further lightwave fibers with respectively one detector for generating at least one error signal (Sr). A piezoelectric deflection unit acts on this front face of the lightwave fiber located in the focusing area of the receiving device.
The novel reception principle, in which the so-called free beam overlay is omitted, does not only result in a simplification of the method for the optimization of the adjustment, but also in a simplification of the optomechanical structure.